Because of the influence on global warming due to refrigerant used in air conditioners, using alternative refrigerant (R32, and HFO refrigerant such as R1234yf and R1234ze) having a small global warming coefficient has been examined instead of using conventional refrigerant (R404A and R410A). In addition, a technique of detecting leaked refrigerant has been examined so that, in an air conditioner, any leak of refrigerant can quickly be detected to take action even if it happens.
With respect to a technique of detecting leaked refrigerant, a technique described in Japanese Patent Application Publication No. 2015-42930 is known. Japanese Patent Application Publication No. 2015-42930 describes an air conditioning apparatus including: an outdoor unit that includes at least a compressor and an outdoor pipe; an indoor unit that includes at least an indoor heat exchanger, an indoor blower fan, and an indoor pipe; an extension pipe that connects the outdoor pipe with the indoor pipe; a first temperature sensor that is disposed below a joining section which connects the indoor heat exchanger with the indoor pipe; and a control section that uses variation in temperature detected by the first temperature sensor while the indoor blower fan is stopped, to determine whether refrigerant having specific gravity larger than that of the indoor air has leaked from the joining section.